Sizing Europe and Big Zeb are among 10 horses left in the sportingbet.com Queen Mother Champion Chase at the Cheltenham Festival.
The respective 2011 and 2010 winners are among 10 horses left in the two-mile feature at the confirmation stage.
Sizing Europe defeated Big Zeb by five lengths 12 months ago to follow up his win in the Arkle Trophy in 2010.
And Henry de Bromhead's stable star got the better of his old rival by 15 lengths in the Tied Cottage Chase at Punchestown last month.
However, Colm Murphy is expecting a better performance from Big Zeb next week.
Willie Mullins has left in the progressive Blazing Tempo, who completed a hat-trick of victories at Fairyhouse, while the Noel Meade-trained Realt Dubh, third in last year's Arkle Trophy, is the other Irish possible.
Heading the home brigade is the Nicky Henderson-trained Finian's Rainbow, who chased home Captain Chris in last year's Arkle.
He was caught close to the finish by Somersby in the Victor Chandler Chase at Ascot last time.
Somersby is, however, more likely to take his chance in the Ryanair Chase on Thursday, unless there is plenty of cut in the ground.
Others standing their ground are Wishfull Thinking, Gauvain, Kauto Stone and I'm So Lucky.
The withdrawn horses were I'msingingtheblues, Jewson Novices' Chase-bound Peddlers Cross, Nacarat and Hold Fast.